Her surrogates- especially here at DU, have stated that more than once.

If HRC does happen to secure for herself the Democratic nomination- she's going to lose the GE and when they point their crooked little index fingers and blame Sanders supporters, they're going to have three other fingers pointing right back at themselves.

Registered Dems are only 29% of voters. Independants are 43%. Republicans about 26%. Polls show Clinton gets only 1/3 of Independants in the GE, Sanders 2/3.
Clinton's GE vote is 1/3 of 43% - 14%, and about 80% of Dems .80 X 29% - 23%. No republicans will crossover for her. She'll get about 40% of popular vote.
Sanders GE vote is 2/3 of Independants, 28%, plus 90% of Dems, 26%, and about 10% crossover from Republicans, 2.5%. 28 + 26 + 2.5 = 56.5% of the GE popular vote.
Although Clinton will still carry the solidly blue states, she will lose every single swing state Obama won by 5 points or less...maybe more. That's not a formula that will win the GE, nor capture down-ticket races.